would be nice to have a separate list of "subscribed threads that I have started" on top of "subscribed threads that I have replied to" as I more interested in replies to my questions than replies (or alternative replies) to my answers and certainly don't want to miss the former once within the subscription list that can get quite long
Then check normal threads via your user control panel that is by clicking settings at top. And for your started threads, Go on thread and click on Thread Tools and subscribe via email so that you get an email whenever someone answers your query in your started thread.
You can already categorize your subscriptions however you want by creating various subscription folders.